The present invention relates to an ink jet head which uses a piezoelectric actuator to discharge ink from a pressure chamber to the outside, a method for producing the same, and an ink jet type recording apparatus incorporating the same.
Ink jet heads which use a piezoelectric actuator to discharge ink from a pressure chamber to the outside are known in the prior art. A conventional ink jet head of this type is disclosed, for example, in Japanese Laid-Open Patent Publication No. 9-232644. As illustrated in FIG. 11, the conventional ink jet head includes a pressure chamber structure member b having a plurality of pressure chambers a which are filled with ink. A common electrode d is provided substantially entirely across one surface (the upper surface in the illustrated example) of the pressure chamber structure member b along which openings c are provided respectively for the pressure chambers a. Piezoelectric layers e and separate electrodes f, which form a piezoelectric actuator together with the common electrode d, are provided at respective positions on the common electrode d corresponding to the openings c of the pressure chambers a. Upon application of a voltage between the common electrode d and one of the separate electrodes f, a corresponding one of the piezoelectric layers e expands/contracts in the planar direction (the horizontal direction in the figure). Since the expansion/contraction of a portion (i.e., the lower portion in the figure) of the piezoelectric layer e on the side of the pressure chamber a is restricted by the common electrode d, the expansion/contraction of the piezoelectric layer e in the planar direction is converted to a displacement in the thickness direction (the vertical direction in the figure). As a result of this conversion, the piezoelectric layer e is displaced in the thickness direction entailing the common electrode d and the separate electrode f, thereby changing the volume of the pressure chamber a so as to discharge the ink from the pressure chamber a to the outside.
Another type of conventional ink jet head uses a restriction plate, in addition to the common electrode d, provided on one of the surfaces of each piezoelectric layer e which are perpendicular to the thickness direction thereof for restricting the expansion/contraction of the piezoelectric layer e in the planar direction on that surface. The expansion/contraction of the piezoelectric layer e in the planar direction is converted by the restriction plate into a displacement in the thickness direction.
In recent years, the popularity of personal computers has rapidly increased. Accordingly, there is an increasing demand for improving the printed image quality as much as possible. For the above-described type of ink jet heads, it is important to improve the performance of the piezoelectric actuator in order to meet the demand.
The present invention has been made in view of such circumstances in the prior art, and has an objective of improving the deformation characteristic of a piezoelectric actuator as much as possible so as to improve the ink discharging capability and thus the printed image quality.
In order to achieve the object described above, according to the first aspect of the present invention, there is provided an ink jet head, including: a pressure chamber structure member including a plurality of pressure chambers which are filled with ink, and a plurality of openings respectively for the pressure chambers which are provided along a predetermined surface of the pressure chamber structure member; and a piezoelectric actuator provided on one surface of the pressure chamber structure member along which the openings of the pressure chambers are provided, wherein: the piezoelectric actuator includes a piezoelectric layer which is provided substantially entirely across one surface of the pressure chamber structure member along which the openings of the pressure chambers are provided and which expands/contracts in a planar direction perpendicular to a thickness direction according to a direction of an electric field applied in the thickness direction; each portion of the piezoelectric actuator which corresponds to the opening of one of the pressure chambers and which generally corresponds to a center of the opening is defined as a displacement section, wherein when an electric field for expanding/contracting the piezoelectric layer in the planar direction is applied across a portion of the piezoelectric layer corresponding to the displacement section, the expansion/contraction of the piezoelectric layer in the planar direction is converted to a displacement in the thickness direction, whereby the displacement section is displaced in the thickness direction as a result of the conversion; each portion of the piezoelectric actuator which corresponds to the opening of one of the pressure chambers and which is in a vicinity of the displacement section is defined as an expansion/contraction section, wherein when an electric field for expanding/contracting the piezoelectric layer in the planar direction is applied across a portion of the piezoelectric layer corresponding to the expansion/contraction section, the expansion/contraction section expands/contracts in the planar direction by the expansion/contraction of the piezoelectric layer in the planar direction; and the displacement of the displacement section in the thickness direction is controlled by the expansion/contraction of the expansion/contraction section in the planar direction, so that the displacement of the displacement section in the thickness direction changes a volume of the corresponding pressure chamber, thereby discharging ink from the pressure chamber to the outside.
With such a structure, upon application of an electric field in the thickness direction of the piezoelectric layer of the piezoelectric actuator, the piezoelectric layer expands/contracts according to the direction of the electric field. Specifically, when the direction of the electric field is the same as the polarization direction of the piezoelectric layer (i.e., from the negative side to the positive side), the piezoelectric layer contracts in the planar direction. When the direction of the electric field is opposite to the polarization direction of the piezoelectric layer, the piezoelectric layer expands in the planar direction.
In either case, in the displacement section (which is defined as a portion of the piezoelectric actuator which corresponds to the opening of one of the pressure chambers and which generally corresponds to the center of the opening), an electric field is applied across the piezoelectric layer in the displacement section, whereby the piezoelectric layer expands/contracts in the planar direction, and the expansion/contraction of the piezoelectric layer in the planar direction is converted into a displacement in the thickness direction, whereby the displacement section is displaced in the thickness direction. The displacement of each displacement section of the piezoelectric actuator in the thickness direction changes the volume of the corresponding pressure chamber, thereby discharging ink from the pressure chamber to the outside.
At this time, in the expansion/contraction section of the piezoelectric actuator provided in the vicinity of each displacement section, an electric field is applied across the piezoelectric layer in the expansion/contraction section, whereby the piezoelectric layer expands/contracts in the planar direction, and the expansion/contraction section is expanded/contracted in the planar direction by the expansion/contraction of the piezoelectric layer in the planar direction. By the expansion/contraction of each expansion/contraction section in the planar direction, the displacement of the corresponding displacement section in the thickness direction is controlled. For example, if the expansion/contraction section expands when the displacement section is displaced from the flat shape into a convex or concave shape, the amount of displacement of the displacement section increases by the amount of expansion of the expansion/contraction section. If expansion/contraction section contracts when the displacement section is displaced from the convex or concave shape into the flat shape, the displacement of the displacement section into the flat shape is facilitated as much as the amount of contraction of the expansion/contraction section. Thus, it is possible to improve the deformation characteristic of the piezoelectric actuator, and to improve the ink discharging capability and thus the printed image quality.
According to the second aspect of the present invention, there is provided an ink jet head as that of the first aspect of the invention, wherein in addition to the piezoelectric layer, the piezoelectric actuator further includes: a common electrode provided at least in each portion of the piezoelectric actuator which corresponds to the opening of one of the pressure chambers on one of surfaces of the piezoelectric layer which are perpendicular to the thickness direction thereof; a separate electrode provided in each displacement section on the other one of the surfaces of the piezoelectric layer which are perpendicular to the thickness direction thereof for producing an electric field of a predetermined direction between the separate electrode and the common electrode; and an auxiliary separate electrode provided in each expansion/contraction section on the same surface of the piezoelectric layer as the separate electrode for producing an electric field of a predetermined direction between the auxiliary separate electrode and the common electrode.
Thus, in each displacement section of the piezoelectric actuator, the piezoelectric layer expands/contracts in the planar direction according to the direction of the electric field which is produced between the separate electrode and the common electrode, and the expansion/contraction of the piezoelectric layer is converted into a displacement in the thickness direction. In each expansion/contraction section, the piezoelectric layer expands/contracts in the planar direction according to the direction of the electric field which is produced between the auxiliary separate electrode and the common electrode. As a result, the function of the first aspect of the invention is realized.
According to the third aspect of the present invention, there is provided an ink jet head as that of the second aspect of the invention, wherein the common electrode is provided substantially entirely across one surface of the pressure chamber structure member along which the openings of the pressure chambers are provided.
According to the fourth aspect of the present invention, there is provided an ink jet head as that of the second aspect of the invention, wherein the common electrode is provided only in each portion of the piezoelectric actuator which corresponds to the opening of one of the pressure chambers.
According to these aspects of the invention, the function of the second aspect of the invention is realized in a desirable manner. Particularly, according to the third aspect of the invention, it is not necessary to divide the common electrode into portions and to provide wirings, or the like, for connecting the common electrode portions together, thereby simplifying the structure.
According to the fifth aspect of the present invention, there is provided an ink jet head as that of the second aspect of the invention, wherein the auxiliary separate electrode is provided only in an area within which the piezoelectric layer can expand/contract in the planar direction.
Thus, the auxiliary separate electrode is not provided in an area where the piezoelectric layer cannot expand/contract, e.g., the area on the pressure chamber structure member excluding the openings, thereby avoiding provision of the auxiliary separate electrode in positions where the auxiliary separate electrode is not necessary. Therefore, the advantageous effects of the second aspect of the invention can be obtained more efficiently.
According to the sixth aspect of the present invention, there is provided an ink jet head as that of the second aspect of the invention, wherein when a voltage is applied between the common electrode and the separate electrode in one displacement section, the voltage producing an electric field of such a direction as to contract the piezoelectric layer in the displacement section, a voltage is applied between the common electrode and the auxiliary separate electrode in each expansion/contraction section corresponding to the displacement section, the voltage producing an electric field of such a direction as to expand the piezoelectric layer in the expansion/contraction section.
Thus, a voltage is applied between the common electrode and the separate electrode in each displacement section so as to produce an electric field of such a direction as to contract the piezoelectric layer in the displacement section. As a result, the piezoelectric layer in the displacement section contracts in the planar direction. At this time, a voltage is applied between the common electrode and the auxiliary separate electrode in the expansion/contraction section corresponding to the displacement section so as to produce an electric field of such a direction as to expand the piezoelectric layer in the expansion/contraction section. Thus, an electric field of the opposite direction to that applied across the displacement section is produced in the expansion/contraction section. Accordingly, the piezoelectric layer in the expansion/contraction section expands as opposed to the displacement section. Thus, the expansion/contraction section expands in the planar direction. As a result, the contraction of the piezoelectric layer in the corresponding displacement section is facilitated as much as the expansion of the expansion/contraction section.
According to the seventh aspect of the present invention, there is provided an ink jet head as that of the second aspect of the invention, wherein when a voltage is applied between the common electrode and the separate electrode in one displacement section, the voltage producing an electric field of such a direction as to expand the piezoelectric layer in the displacement section, a voltage is applied between the common electrode and the auxiliary separate electrode in each expansion/contraction section corresponding to the displacement section, the voltage producing an electric field of such a direction as to expand the piezoelectric layer in the expansion/contraction section.
Thus, a voltage is applied between the common electrode and the separate electrode in each displacement section and between the common electrode and the auxiliary separate electrode in the expansion/contraction section corresponding to the displacement section so as to produce an electric field of such a direction as to expand the piezoelectric layer both in the displacement section and the expansion/contraction section. As a result, the expansion of the expansion/contraction section is added to the expansion of the displacement section itself, whereby the displacement in the thickness direction of the piezoelectric layer in the displacement section is greater than that provided by only the expansion of the displacement section itself.
According to the eighth aspect of the present invention, there is provided an ink jet head as that of the seventh aspect of the invention, wherein the auxiliary separate electrode in each expansion/contraction section is provided to be integral with the separate electrode in the corresponding displacement section.
Thus, if the direction of the electric field produced between the common electrode and the separate electrode in each displacement section is the same as the direction of the electric field produced between the common electrode and the auxiliary separate electrode in the corresponding expansion/contraction section, as in the seventh aspect of the invention, the separate electrode and the auxiliary separate electrode are provided with the same potential direction (positive/negative) with respect to the common electrode. Since the auxiliary separate electrode is integral with the separate electrode, the same voltage application means can be used as means for applying a voltage between the common electrode and the separate electrode in each displacement section and also as means for applying a voltage between the common electrode and the auxiliary separate electrode in each expansion/contraction section. Therefore, the advantageous effects of the seventh aspect of the invention can be obtained more efficiently.
According to the ninth aspect of the present invention, there is provided an ink jet head, including: a pressure chamber structure member including a plurality of pressure chambers which are filled with ink, and a plurality of openings respectively for the pressure chambers which are provided along a predetermined surface of the pressure chamber structure member; and a piezoelectric actuator provided on one surface of the pressure chamber structure member along which the openings of the pressure chambers are provided, wherein: the piezoelectric actuator includes: a piezoelectric layer which is provided substantially entirely across one surface of the pressure chamber structure member along which the openings of the pressure chambers are provided and which expands/contracts in a planar direction perpendicular to a thickness direction according to a direction of an electric field applied in the thickness direction; a common electrode provided on one of surfaces of the piezoelectric layer which are perpendicular to the thickness direction thereof; and a separate electrode provided on the other one of the surfaces of the piezoelectric layer which are perpendicular to the thickness direction thereof for producing the electric field of a predetermined direction between the separate electrode and the common electrode; a restriction plate for restricting expansion/contraction in the planar direction of a portion of the piezoelectric layer on one side thereof which is closer to the pressure chamber structure member is provided in each portion of the piezoelectric actuator which corresponds to the opening of one of the pressure chambers on one surface of the piezoelectric actuator which is closer to the pressure chamber structure member; and the expansion/contraction of the piezoelectric layer in the planar direction is converted by the restriction plate into a displacement in the thickness direction thereof to displace in the thickness direction a portion of the piezoelectric actuator which corresponds to the opening of the pressure chamber so as to change a volume of the corresponding pressure chamber, thereby discharging ink from the pressure chamber to the outside.
According to this aspect of the invention, the piezoelectric layer of the piezoelectric actuator is provided substantially entirely across the surface of the pressure chamber structure member. Therefore, the electrical insulation between the common electrode and the separate electrode along the thickness direction is reliably ensured by the piezoelectric layer. As a result, an electrical discharge between these electrodes is less likely to occur as compared to a case where the piezoelectric layer is provided only in a portion of the piezoelectric actuator corresponding to the opening of each of the pressure chambers. Thus, by providing the piezoelectric layer substantially entirely across the surface of the pressure chamber structure member, it is possible to prevent the deformation characteristic of the piezoelectric actuator from deteriorating due to an electrical discharge, or the like, between the common electrode and the separate electrode. Moreover, when the piezoelectric layer is provided substantially entirely across the surface of the pressure chamber structure member, the portion of the piezoelectric actuator for displaceably supporting a portion of the piezoelectric layer which is displaced in the thickness direction (the portion of the piezoelectric actuator surrounding the displacement section) is formed by the piezoelectric layer in addition to the common electrode. Therefore, the thickness of such a portion is increased by the thickness of the piezoelectric layer, and the piezoelectric actuator may become less flexible, thereby deteriorating the deformation characteristic thereof. However, according to this aspect of the invention, the restriction plate is provided in each portion of the piezoelectric actuator which corresponds to the opening of one of the pressure chambers. Therefore, the restriction plate does not need to be provided in the support section. Moreover, the common electrode does not need to function as a restriction plate. Accordingly, the common electrode can be made more flexible. Thus, the flexibility of the support section is not reduced, thereby suppressing the possible deterioration in the deformation characteristic of the piezoelectric actuator. Therefore, as in the first aspect of the invention, it is possible to improve the deformation characteristic of the piezoelectric actuator as much as possible, and to improve the ink discharging capability and thus the printed image quality.
According to the tenth aspect of the present invention, there is provided an ink jet head as that of the ninth aspect of the invention, wherein the separate electrode is provided on the surface of the piezoelectric layer which is away from the pressure chamber structure member.
Thus, the common electrode is located on the side of the piezoelectric layer which is closer to the pressure chamber structure member, and can be provided substantially entirely across the surface of the pressure chamber structure member, thereby facilitating and making more reliable the support for the portion which deforms.
According to the eleventh aspect of the present invention, there is provided an ink jet head as that of the ninth aspect of the invention, wherein an electrically insulative layer is provided substantially entirely across the surface of the piezoelectric actuator which is closer to the pressure chamber structure member; and each restriction plate is secured to the piezoelectric actuator via the electrically insulative layer.
With no additional measure taken, the electrode on the side of the piezoelectric layer which is closer to the pressure chamber structure member contacts the ink contained in the pressure chamber. Ink used in an ink jet head is typically water-soluble. Therefore, with no additional measure taken, the potential of the electrode is changed to the ground side via the ink. For example, if the electrode is the separate electrode of the present invention, the potentials of all of such separate electrodes will transition to the same potential via the ink. Even when the electrode is the common electrode of the present invention, if a positive or negative potential is applied to the common electrode, the potential of the common electrode is reduced or increased toward the ground side potential. However, according to this aspect of the invention, the electrode on the side of the piezoelectric layer which is closer to the pressure chamber structure member is electrically insulated by the electrically insulative layer from the ink contained in the ink pressure chamber, thus avoiding such a problem. Moreover, when the separate electrode is located on the side of the piezoelectric layer closer to the pressure chamber structure member, it is possible to prevent the piezoelectric layer from deteriorating due to a direct contact with the ink contained in the pressure chamber.
According to the twelfth aspect of the present invention, there is provided an ink jet head as that of the ninth aspect of the invention, wherein: the pressure chamber structure member and the piezoelectric actuator are bonded together via an intermediate structure member which is provided to be integral with the piezoelectric actuator; and the intermediate structure member is made of the same material as the restriction plate.
When the pressure chamber structure member and the piezoelectric actuator are bonded together via the intermediate structure member which is provided to be integral with the piezoelectric actuator, the production process would require a separate step for providing the intermediate structure member. However, according to this aspect of the invention, the intermediate structure member is made of the same material as the restriction plate. Therefore, when the restriction plate having a predetermined shape is provided from a restriction plate layer as will be described below as the sixteenth aspect of the invention, the intermediate structure member can be provided from the same restriction plate layer and simultaneously with the restriction plate. As a result, unlike when the intermediate structure member is made of a material different from that of the restriction plate, there is no need for a step of providing a separate intermediate structure member layer or a step of providing the intermediate structure member from the intermediate structure member layer. Thus, it is possible to suppress the possible increase in the number of steps for producing the ink jet head.
According to the thirteenth aspect of the present invention, there is provided an ink jet head as that of the ninth aspect of the invention, wherein the pressure chamber structure member and the piezoelectric actuator are bonded together via an intermediate structure member which is provided to be integral with the piezoelectric actuator by means of an electro-deposition resin; and the intermediate structure member is made of an electrically conductive material and functions as an electro-deposition electrode for electro-deposition of the electro-deposition resin onto the intermediate structure member.
When the pressure chamber structure member and the piezoelectric actuator are bonded together via the intermediate structure member by means of the electro-deposition resin, it is necessary during the production process to electro-deposit the electro-deposition resin onto one of the junction plane between the pressure chamber structure member and the intermediate structure member and the junction plane between the piezoelectric actuator and the intermediate structure member. This requires a separate electrode for electro-deposition to be provided on the side which is to be subjected to electro-deposition. However, according to this aspect of the invention, the intermediate structure member is made of an electrically conductive material, whereby the electro-deposition process can be performed by using the intermediate structure member as an electro-deposition electrode, thus eliminating the need for providing a separate electro-deposition electrode.
According to the fourteenth aspect of the present invention, there is provided a method for producing an ink jet head, the ink jet head including: a piezoelectric actuator including a piezoelectric layer which expands/contracts in a planar direction perpendicular to a thickness direction according to a direction of an electric field applied in the thickness direction, wherein the expansion/contraction of the piezoelectric layer in the planar direction is converted into a displacement in the thickness direction by a restriction plate for restricting the expansion/contraction on one of surfaces of the piezoelectric layer which are perpendicular to the thickness direction, thereby discharging ink from the pressure chamber to the outside.
According to this aspect of the invention, the method includes the steps of: providing a piezoelectric actuator on a substrate; providing a restriction plate layer on the piezoelectric actuator so as to substantially entirely cover the surface of the piezoelectric actuator; patterning the restriction plate layer into a predetermined pattern so as to provide a plurality of restriction plates from the restriction plate layer, thereby providing an intermediate product which includes the piezoelectric actuator and the restriction plates being provided on the substrate; bonding the intermediate product to a pressure chamber structure member which includes a plurality of pressure chambers so that the restriction plates are located on the side of the intermediate product which is closer to the pressure chamber structure member and the restriction plates respectively correspond to the pressure chambers; and removing the substrate from the intermediate product on the pressure chamber structure member.
According to this aspect of the invention, in the production of an ink jet head, the piezoelectric actuator bonded to the pressure chamber structure member is provided on the substrate along with the restriction plate. Specifically, after the piezoelectric actuator is provided on the substrate, the restriction plate layer is provided on the piezoelectric actuator so as to substantially entirely cover the surface of the piezoelectric actuator. Then, a plurality of restriction plates are provided from the restriction plate layer. Thus, an intermediate product is obtained which includes the piezoelectric actuator and the restriction plates being provided on the substrate. The intermediate product is bonded to the pressure chamber structure member so that the restriction plates are on the side closer to the pressure chamber structure member. Then, the substrate is removed from the intermediate product on the pressure chamber structure member. Thus, the ink jet head according to the ninth aspect of the invention can be easily obtained.
According to the fifteenth aspect of the present invention, there is provided a method for producing an ink jet head as that of the fourteenth aspect of the invention, wherein after providing the piezoelectric actuator on the substrate, an electrically insulative layer is provided on the piezoelectric actuator so as to substantially entirely cover the surface of the piezoelectric actuator; and after providing the electrically insulative layer, the restriction plate layer is provided on the electrically insulative layer.
Thus, before providing the restriction plate layer on the piezoelectric actuator on the substrate, the electrically insulative layer is provided on the piezoelectric actuator, and the restriction plate layer is provided on the electrically insulative layer. Therefore, the ink jet head according to the eleventh aspect of the invention can be easily obtained.
According to the sixteenth aspect of the present invention, there is provided a method for producing an ink jet head as that of the fourteenth aspect of the invention, wherein an intermediate structure member is provided from the restriction plate layer simultaneously while providing the restriction plates from the restriction plate layer; and after providing the intermediate structure member, the intermediate product and the pressure chamber structure member are bonded together via the intermediate structure member.
Thus, in the case where the pressure chamber structure member and the piezoelectric actuator are bonded together via the intermediate structure member which is provided to be integral with the piezoelectric actuator, when the restriction plates are provided on the piezoelectric actuator from the restriction plate layer, the intermediate structure member is simultaneously provided also from the restriction plate layer. Therefore, the ink jet head according to the twelfth aspect of the invention can be easily obtained.
According to the seventeenth aspect of the present invention, there is provided a method for producing an ink jet head as that of the sixteenth aspect of the invention, wherein when providing the restriction plate layer, an electrically conductive material is used as a material of the restriction plate layer; after providing the restriction plates and the intermediate structure member from the restriction plate layer, an electro-deposition resin is electro-deposited onto the intermediate structure member by using the intermediate structure member as an electro-deposition electrode; and after the electro-deposition of the electro-deposition resin, the intermediate product and the pressure chamber structure member are bonded together by the electro-deposition resin on the intermediate structure member.
Thus, in the case where the pressure chamber structure member and the intermediate product are bonded together by the electro-deposition resin, an electrically conductive material is used as the material of the restriction plate layer. After the restriction plates and the intermediate structure member are provided simultaneously from the restriction plate layer, the electro-deposition resin is electro-deposited onto the intermediate structure member by using the intermediate structure member as an electro-deposition electrode. Therefore, the ink jet head according to the thirteenth aspect of the invention can be easily obtained.
According to the eighteenth aspect of the present invention, there is provided a method for producing an ink jet head, the ink jet head including: a piezoelectric layer which expands/contracts in a planar direction perpendicular to a thickness direction according to a direction of an electric field applied in the thickness direction, wherein the expansion/contraction of the piezoelectric layer in the planar direction is converted into a displacement in the thickness direction, thereby discharging ink from the pressure chamber to the outside, the method including the steps of: providing a common electrode on a substrate substantially entirely across the surface of the substrate; providing a piezoelectric layer on the common electrode substantially entirely across the surface of the common electrode; providing a separate electrode layer on the piezoelectric layer substantially entirely across the surface of the piezoelectric layer; patterning the separate electrode layer into a predetermined pattern so as to provide a plurality of separate electrodes from the separate electrode layer; and providing a plurality of pressure chambers in the substrate so that the pressure chambers respectively correspond to the separate electrodes.
Thus, the common electrode, the piezoelectric layer and the separate electrode layer are provided in this order on the substrate substantially entirely across the surface of the substrate, after which a plurality of separate electrodes are provided from the separate electrode layer. After the plurality of separate electrodes are provided, a plurality of pressure chambers are provided on the substrate so as to respectively correspond to the separate electrodes. As a result, the substrate becomes a pressure chamber structure member, and the common electrode and the piezoelectric layer are provided substantially entirely across the surface of the pressure chamber structure member. With such a production method, the piezoelectric layer can be provided as a thin film by using a sputtering method, whereby it is possible to stabilize the thickness and also to improve the stress resisting property thereof. As a result, it is possible to easily and stably produce a piezoelectric actuator which has a high flexibility and a high mechanical strength. Moreover, as in the ninth aspect of the invention, it is possible to suppress the possible electrical discharge between the common electrode and the separate electrode. Thus, it is possible to improve the deformation characteristic of the piezoelectric actuator as much as possible, and to improve the ink discharging capability and thus the printed image quality.
According to the nineteenth aspect of the present invention, there is provided an ink jet type recording apparatus for performing a recording operation by discharging ink from an ink jet head onto a recording medium, wherein: the ink jet head includes: a pressure chamber structure member, the pressure chamber structure member including a plurality of pressure chambers which are filled with ink and a plurality of openings respectively for the pressure chambers which are provided along a predetermined surface of the pressure chamber structure member; and a piezoelectric actuator provided on one surface of the pressure chamber structure member along which the openings of the pressure chambers are provided; the piezoelectric actuator includes a piezoelectric layer which is provided substantially entirely across one surface of the pressure chamber structure member along which the openings of the pressure chambers are provided and which expands/contracts in a planar direction perpendicular to a thickness direction according to a direction of an electric field applied in the thickness direction; each portion of the piezoelectric actuator which corresponds to the opening of one of the pressure chambers and which generally corresponds to a center of the opening is defined as a displacement section, wherein when an electric field for expanding/contracting the piezoelectric layer in the planar direction is applied across a portion of the piezoelectric layer corresponding to the displacement section, the expansion/contraction of the piezoelectric layer in the planar direction is converted to a displacement in the thickness direction, whereby the displacement section is displaced in the thickness direction as a result of the conversion; each portion of the piezoelectric actuator which corresponds to the opening of one of the pressure chambers and which is in a vicinity of the displacement section is defined as an expansion/contraction section, wherein when an electric field for expanding/contracting the piezoelectric layer in the planar direction is applied across a portion of the piezoelectric layer corresponding to the expansion/contraction section, the expansion/contraction section expands/contracts in the planar direction by the expansion/contraction of the piezoelectric layer in the planar direction; and the ink jet head is configured so that the displacement of the displacement section in the thickness direction is controlled by the expansion/contraction of the expansion/contraction section in the planar direction, so that the displacement of the displacement section in the thickness direction changes a volume of the corresponding pressure chamber, thereby discharging ink from the pressure chamber onto the recording medium.
According to this aspect of the invention, advantageous effects as those of the first aspect of the invention can be obtained.
According to the twentieth aspect of the present invention, there is provided an ink jet type recording apparatus for performing a recording operation by discharging ink from an ink jet head onto a recording medium, wherein: the ink jet head includes: a pressure chamber structure member, the pressure chamber structure member including a plurality of pressure chambers which are filled with ink and a plurality of openings respectively for the pressure chambers which are provided along a predetermined surface of the pressure chamber structure member; and a piezoelectric actuator provided on one surface of the pressure chamber structure member along which the openings of the pressure chambers are provided; the piezoelectric actuator includes: a piezoelectric layer which is provided substantially entirely across one surface of the pressure chamber structure member along which the openings of the pressure chambers are provided and which expands/contracts in a planar direction perpendicular to a thickness direction according to a direction of an electric field applied in the thickness direction; a common electrode provided on one of surfaces of the piezoelectric layer which are perpendicular to the thickness direction thereof; and a separate electrode provided on the other one of the surfaces of the piezoelectric layer which are perpendicular to the thickness direction thereof for producing the electric field of a predetermined direction between the separate electrode and the common electrode; a restriction plate for restricting expansion/contraction in the planar direction of a portion of the piezoelectric layer on one side thereof which is closer to the pressure chamber structure member is provided in each portion of the piezoelectric actuator which corresponds to the opening of one of the pressure chambers on one surface of the piezoelectric actuator which is closer to the pressure chamber structure member; and the ink jet head is configured so that the expansion/contraction of the piezoelectric layer in the planar direction is converted by the restriction plate into a displacement in the thickness direction thereof to displace in the thickness direction a portion of the piezoelectric actuator which corresponds to the opening of the pressure chamber so as to change a volume of the corresponding pressure chamber, thereby discharging ink from the pressure chamber onto the recording medium.
Thus, advantageous effects as those of the ninth aspect of the invention can be obtained.